Electron shells in atoms
antisymmetry=> Pauli Principle=>filling up shells after all the quantum numbers are used up (can’t make an antisym w/o quantum numbers to flip=>u1u2-u2u1=0)
n=1,l=0, two states from spin, shell filled, He (called shell because prob. peaks at r)
n=2, l=0,1, Li and Be use up the l=0,
l=1 (3m’s)x2spin states, B,C,N,O,F,Ne- -shell filled with next “noble element”
next element, Na, has an n=3, l=0 electron sitting outside the shell, acts like hydrogen electron, etc. (beyond atomic number Z=46, the spin-orbit energy is no longer a small effect, and the pattern gets more complicated, and beyond 58 is complex)